Refraction, Binocular Vision, and Accommodation
The refraction, binocular vision, and accommodation domain asks you to choose and interpret tests, then connect the numbers to a diagnosis and a plan. Expect items on endpoint refinement, AC/A, fusional reserves, and accommodative dysfunction.
Refraction endpoints
Retinoscopy first, then fogging to relax accommodation. Refine cylinder with the Jackson cross cylinder in 0.25 D steps, flipping to compare; refine axis with the same lens at the estimated axis, then recheck power. Use duochrome as a spherical check: red clearer means add minus, green clearer means add plus (RAM-GAP). Balance the eyes binocularly at the end, and compare subjective acuity with objective findings.
Binocular and accommodative testing
Cover test at distance and near establishes the deviation; then measure NPC, BI/BO fusional ranges, and stereopsis. AC/A by the gradient method (change in deviation per 1 D of added lens) or calculated from IPD and near fixation distance. Amplitude of accommodation compared with Hofstetter's minimum (15 − 0.25 × age) identifies insufficiency; ±2.00 D flipper facility assesses accommodative dynamics. NRA and PRA bracket the near add.
Worked example
A 34-year-old reports near asthenopia. Distance refraction is plano; cover test is ortho at distance and 8 prism diopters exo at near; NPC breaks at 15 cm; near BO break is 10; PRA is −1.50, NRA +2.50; calculated AC/A is 4. Interpretation: convergence insufficiency - exo at near exceeding distance, remote NPC, reduced positive fusional reserves, normal AC/A. Plan: office-based vergence therapy as first line (home pencil push-ups alone are weaker), plus a small near add for immediate relief, and recheck in 8 to 12 weeks with repeat NPC and BO ranges.
Traps
Treating a deviation before correcting uncorrected hyperopia; accepting a subjective endpoint without fogging; dismissing a low PRA as "just accommodation"; and prescribing an add by age alone instead of by working distance and NRA/PRA balance.